Electric motor for a water pump

ABSTRACT

An electric coolant or water pump with a housing including and a housing sleeve adapted to receive a bearing assembly. An integral shaft bearing assembly is mounted inside the housing sleeve. The integral shaft bearing assembly includes a shaft, an outer bearing ring, and at least one bearing located between the shaft and the outer bearing ring. An impeller is connected to the shaft and located in the pump chamber. An electric motor is mounted to the housing, with the electric motor including a stator connected to an outside of the housing sleeve and a rotor mounted to the shaft on an opposite end from the impeller. The rotor is located opposite from and rotatable relative to the stator.

INCORPORATION BY REFERENCE

The following documents are incorporated herein by reference as if fully set forth: U.S. Provisional Application No. 62/008,105, filed Jun. 5, 2015.

FIELD OF INVENTION

The present invention relates to an integrated electric motor/pump assembly, and in particular, an electric motor driven water pump for use in a cooling system in a vehicle.

BACKGROUND

It is known to use electric motors for driving water pumps. However, in many cases the electric motor driven water pump includes a hydrodynamic bearing which does not provide an accurate axial location and has more friction than other types of bearings, i.e., rolling bearings. Additionally, most electric motors include an inner rotor mounted on a bearing supported shaft, that is surrounded by the stator. This either results in increased axial length for the water pump or may require the use of non-standard bearings, making the water pump more costly. A further issue with most electric water pump motors is that they require non-standard mounting and/or packaging in the engine compartment for internal combustion engines. Mounting or replacing the electric motor bearings on the shaft in the known conventional electric water pumps is also time and labor consuming.

It would be desirable to provide an improved electric water pump with an integrated electric motor.

It would also be desirable to provide an electric water pump with fewer parts than a conventional electric water pump and that is more axially compact to reduce the space required for the water pump in an engine compartment or other location in a vehicle. Further, it would be desirable to provide an improved bearing arrangement other than the known hydrodynamic bearings.

SUMMARY

Briefly stated, an electric pump assembly, preferably for water or coolant, is provided including a housing and a housing sleeve adapted to receive a bearing assembly connected to the housing. An integral shaft bearing assembly is mounted inside the housing sleeve. The integral shaft bearing assembly includes a shaft, an outer bearing ring, and at least one bearing element, preferably in the form of a row of rolling elements, located between the shaft and the outer bearing ring. An impeller is connected to the shaft and located in the pump chamber. An electric motor is mounted to the housing, with the electric motor including a stator connected to an outside of the housing sleeve and a rotor mounted to the shaft on an opposite end from the impeller. The rotor is located opposite from and rotatable relative to the stator.

This arrangement allows for the use of an integral shaft bearing assembly which takes less space and has reduced tolerances than the prior known hydrodynamic bearings. The integral shaft bearing assembly is used in connection with a mechanical seal located between the housing and the shaft so that the bearing is isolated from the cooling fluid or other fluid carried by the pump. This can result in longer bearing life and higher accuracy for the axial position of the shaft due to the use of a rolling bearing versus hydrodynamic bearing. Further, due to the use of the integral shaft bearing assembly, repair and replacement of the bearing is less time consuming and easier to achieve.

In one aspect, the housing also includes a pump chamber with an inlet, an outlet. However, this is not required.

In another aspect, the rotor is cup-shaped and extends from the opposite end of the shaft about the housing sleeve so that the rotor is located outside of and rotates about the stator. Preferably, the stator includes a stator iron connected to the outside of the housing sleeve.

In another aspect, the integral shaft bearing assembly includes two rows of rolling elements located between the shaft and the outer bearing ring. The rolling elements are preferably separated by cages. Alternatively, plain bearings can be utilized with a separate axial stop. Preferably, bearing seals are located between the shaft and the outer bearing ring at each of the bearings to prevent ingress of debris into the bearings of the ISB.

In one embodiment, the rotor may include an integrated cooling fan located in an axial end surface thereof. Preferably, permanent magnets are also connected to the rotor located in a cylindrical portion thereof that surrounds the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings:

FIG. 1 is a perspective view, partially in cross-section, of an electric water pump according to the invention.

FIG. 2 is a perspective, cross-sectional view similar to FIG. 1 of a second embodiment of an electric water pump according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Certain terminology is used in the following description for convenience only and is not limiting. The words “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from the parts referenced in the drawings. “Axially” refers to a direction along the axis of a shaft or rotating part. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, or c, or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof and words of similar import.

Referring to FIG. 1, an electric pump assembly 10, preferably for water or coolant, according to the present invention is shown. The electric pump assembly 10 integrates an electric motor 40 with the pump housing 12 to form a single electric pump unit 10. A preferred application is for an electric water or coolant pump for a motor vehicle, and the electric pump is also referred to as an electric water pump assembly herein, without being limiting. The electric water pump assembly 10 includes the housing 12, and can include a pump chamber 13 located therein with an inlet 14 and an outlet 16, and a housing sleeve 32 adapted to receive a bearing assembly. Alternatively, the housing 12 can just include the housing sleeve 32 and a cover portion adapted to close the volute chamber that receives the impeller that is formed on the mating component of the engine. The sleeve 32 could optionally be formed as a separate component that is connected to the housing 12. The inlet and outlet can also be located on the mating component of the engine. The housing 12 is preferably a cast or machined aluminum part and/or can be formed by a sintered material to a near net shape. Other materials can be utilized, for example cast iron or plastic.

An integral shaft bearing assembly (ISB) 20 is mounted inside the housing sleeve 32. The ISB 20 includes a shaft 22 and outer bearing ring 30 and at least one bearing element, preferably in the form of at least one row of rolling elements 24A, 24B located between the shaft 22 and the outer bearing ring 30. As shown in FIG. 1, preferably two bearing elements 24A, 24B are provided between the shaft 22 and the outer bearing ring 30. The bearing elements 24A, 24B are preferably rows of rolling elements, and more preferably ball bearings or rollers and include rolling elements separated by cages 26A, 26B, and the shaft 22 preferably includes grooves that act as inner races for the rolling elements. As shown in FIG. 1, preferably bearing seals 28A, 28B are located between the shaft 22 and the outer bearing ring 30 in proximity to each of the bearings 24A, 24B. The ISB 20, including the shaft 22, outer bearing ring 30, bearings 24A, 24B with cages 26A, 26B, and the bearing seals 28A, 28B, is preferably a pre-assembled unit and can be installed as a single part into the electric water pump assembly 10. Preferably, the ISB 20 is pressed into the housing sleeve 32.

Further, a seal 34 is preferably located between the shaft 22 and the housing 12. The seal separates the bearing element(s) 24A, 24B from the pump chamber 13 and any fluid being carried by the pump. The seal 34 can be a mechanical seal, a lip seal, or other suitable seal arrangement to prevent the ingress of coolant being handled by the pump. This is important to increase the life of the bearings.

Still with reference to FIG. 1, an impeller 18 is connected to the shaft 22 and located in the pump chamber 13. As shown in FIG. 1, the impeller 18 is preferably a centrifugal impeller which takes fluid from the inlet 14 and forces it radially outwardly in a given rotational direction such that the fluid exits the pump chamber 13 via the outlet 16 to be circulated, for example, in a cooling system of a vehicle, which could be an electric vehicle or a vehicle with an internal combustion engine. This can be used, for example, for cooling an electric motor in the electric vehicle or for cooling a battery compartment.

The electric motor 40 is mounted to the housing 12. The electric motor 40 includes a stator formed by a stator iron 42 as well as a stator coil 44 connected to an outside of the housing sleeve 32. A rotor 46 is mounted to the shaft 22 on an opposite end from the impeller 18. The rotor 46 is located outside of and rotatable about the stator parts 42, 44. Preferably, the rotor 46 is cup-shaped and includes an axial disc portion 47 as well as a cylindrical portion 49 that extends circumferentially about the stator parts 42, 44. Rotor magnets 50 are preferably located on the cylindrical portion 49 of the rotor 46. Using the cup-shaped rotor 46, which extends from the opposite end of the shaft 22 from the impeller 18 about the housing sleeve 32 and the ISB 20 located therein, a reduction in the overall axial length of the electric water pump 10 is achieved in comparison with the known conventional electric water pumps. Further, as both the stator parts 42, 44 as well as the rotor 46 are located outside of the housing 12, this totally separates the electric motor 40 components from the fluid carrying portion of the water pump housing 12. This arrangement provides fewer parts and a more compact assembly than conventional water pumps. This arrangement also allows for easier maintenance for replacement of the ISB 20 as well as possibly also the coils or magnets as a unit when replacing or rebuilding a water pump assembly 10.

Referring now to FIG. 2, second embodiment of an electric pump assembly 10′ is shown. The electric pump assembly 10′ is the same as the electric pump assembly 10 except that here optional cooling fan fins 48 have been punched into the axial disc portion 47. This provides for cooing of the electric rotor 40 without the need for a separate fan since the fins 48 are stamped into the rotor 46.

In either embodiment of the electric water pump assembly 10, 10′, the stator 42, 44 located outside of the housing 12 on the housing sleeve 32 is supplied with commutated power in order to rotate the rotor 46 in order to drive the shaft 22 to rotate the pump impeller 18. Accordingly, a compact electric water pump 10, 10′ is provided having fewer parts and a more compact arrangement, specifically in the axial direction, than prior known conventional electric water pumps.

Having thus described the present invention in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description of the invention, could be made without altering the inventive concepts and principles embodied therein. It is also to be appreciated that numerous embodiments incorporating only part of the preferred embodiment are possible which do not alter, with respect to those parts, the inventive concepts and principles embodied therein. The present embodiment and optional configurations are therefore to be considered in all respects as exemplary and/or illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all alternate embodiments and changes to this embodiment which come within the meaning and range of equivalency of said claims are therefore to be embraced therein. 

What is claimed is:
 1. An electric pump, comprising: a housing, and a housing sleeve adapted to receive a bearing assembly connected to the housing; an integral shaft bearing assembly mounted inside the housing sleeve, the integrated shaft bearing assembly including a shaft, an outer bearing ring, and at least one bearing element located between the shaft and the outer bearing ring; an impeller connected to the shaft and located in the pump chamber; an electric motor mounted to the housing, the electric motor including a stator connected to an outside of the housing sleeve and a rotor mounted to the shaft on an opposite end from the impeller, the rotor being located opposite from and being rotatable relative to the stator.
 2. The electric pump of claim 1, wherein the rotor is cup-shaped and extends from the opposite end of the shaft about the housing sleeve.
 3. The electric pump of claim 1, wherein the stator includes a stator iron connected to an outside of the housing sleeve.
 4. The electric pump of claim 1, wherein the at least one bearing element comprises a row of rolling elements.
 5. The electric pump of claim 4, wherein the shaft includes a bearing raceway for the row of rolling elements.
 6. The electric pump of claim 4, wherein the rolling elements are separated by cages.
 7. The electric pump of claim 1, wherein the integral shaft bearing assembly includes two rows of rolling elements as the at least one bearing element located between the shaft and the outer bearing ring.
 8. The electric pump of claim 7, further comprising bearing seals located between the shaft and the outer bearing ring located at each of the rows of rolling elements.
 9. The electric pump of claim 1, further comprising a seal located between the shaft and the housing, separating the at least one bearing element from the pump chamber.
 10. The electric pump of claim 1, wherein the rotor includes an integrated cooling fan.
 11. The electric pump of claim 1, further comprising permanent magnets connected to the rotor.
 12. The electric pump of claim 1, wherein the housing includes a pump chamber, an inlet and an outlet.
 13. The electric pump of claim 1, wherein the rotor is located outside of and rotatable relative to about the stator.
 14. The electric pump of claim 1, wherein the pump is for a coolant. 